1. Field of the Invention
The present invention relates in general to a an electroencephalographic electrode or probe used for sensing the potential of skin and in particular to a self-preparing electrode or probe which is easily and securely held in place with little preparation of the patient, thus facilitating electroencephalographic mapping.
2. Description of the Related Art
Electroencephalograms and electrocardiograms are commonly performed on medical patients by sensing the potential of skin covering the brain and heart, respectively. An electroencephalogram (hereinafter EEG), is prepared by placing one or more electrodes in electrical contact with the blood-rich epidermis layer of skin on the scalp and connecting a reference lead, for example, to an ear lobe. The electrode(s) and refrence lead are connected to an amplifier and other equipment which use the signals sensed by the electrodes to prepare the EEG.
A conventional EEG electrode, Part No. H304075 manufactured by Beckman, is illustrated in FIGS. 1A and 1B. The surface of the conventional EEG electrode which makes contact with the scalp is illustrated in FIG. 1A. To make contact with blood-rich epidermis layer of the skin, a portion of the scalp is shaved to remove hair and dead skin or keratinous layer is scraped or abraded away at the point at which the electrode is to be attached. An adhesive is placed on the outer circular surface 10 and an electrolyte cream or gel is placed in the center 12. As indicated by the cross-section of the conventional EEG electrode, illustrated in FIG. 1B, the center 12 is indented or set back from the surface 10. A silver plug 14 is surrounded by a plastic cover 16 on three sides and is exposed only on the surface 12 where the electrolyte gel is applied. A wire 18 is connected to the silver plug 14 for making connections to an electroencephalograph.
While the conventional EEG electrode is satisfactory for many applications, it has several drawbacks, especially when used for EEG mapping in which electrodes are attached at many points on a scalp. Since the conventional electrode requires shaving of the area to which the electrode is attached and removal of dead skin, large areas of a patient's head must be shaved and the patient experiences the discomfort of the abrasion process during EEG mapping using the conventional electrode. In addition, conventional electrodes can be inadvertently released from a patient's head due to movement or deterioration of the adhesive and the adhesive must be removed between applications in order to ensure proper contact. Finally, no shielding is provided for the electrode or wire with the result that electromagnetic waves of many frequencies, such as 60 Hz must be eliminated from the signal produced by the EEG electrode via the electroencephalograph or an amplifier used in conjunction therewith.